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Old cast iron radiators

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joseph annon
joseph annon Member Posts: 53
I am currently working on a remodel of a home that has Crane cast iron radiators. The inspector is requesting and air test on the radiators at 60PSI.

To clarify where I am (Santa Fe New Mexico) cast iron radiators are rare and steam even rarer especially in residences. So I do have a lot of experience with cast iron radiators other that servicing boilers on water radiators.

What are your experiences in these cases? Am I going to see air leaks in the system due the pressure being 5X what the system has seen?

We are also shortening a coupling of radiator runs. What should I look for in the radiator push nipple connectors while doing this alteration.

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  • Jamie Hall
    Jamie Hall Member Posts: 23,523
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    I can't guarantee you will see leaks at 60 psi -- but I'd be real surprised if you didn't. The real question, though, is were these steam or hot water? And if hot water, what is the pressure relief valve setting? if it's the standard 30 psi, you do need a pressure test at twice the relief valve setting.

    However, if at all possible, persuade him to let you test with water, not air. Please. Air is easier, I'll grant you. However, if there is a crack or defect, and it lets go, you are in a world of hurt if you are anywhere in the vicinity -- whereas with water all you are is wet.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ironman
    Ironman Member Posts: 7,385
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    That’s way too much pressure on the rads.

    The inspector needs to use a little common sense and realize that those rads were never meant to take that kind of pressure anymore than the boiler could. If the rads are presently connected, why is a pressure test required? You can’t apply today’s code to something that’s been there for 100 years.

    If you’re running new piping to them, only the new piping should be required to be tested.

    If you’re shortening radiator lengths, you could have push or threaded nipples. If there are no draw rods, the rad will have threaded nipples and you’ll probably need a machine shop to deal with them. If they have push nipples, you may still need a machine shop to make new ones if the old ones are pitted.

    I’ve had to deal with a local inspector who could be a little too aggressive, and who would invent requirements not in the code about pressurizing old rads, and he finally came to agree that 30 psi was all that was needed.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • joseph annon
    joseph annon Member Posts: 53
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    They are cast iron hot water baseboards. Made by Crane and are type R baseboards. There are signs that the coin vents leaked (corrosion). I did ask if I could use a water test instead of air. Inspector said they would be OK with 60PSi air. Relief valve will be 30 PSI. I will mention to him the possibility of catastrophic failure under air and see if he will let me do a water test. The areas where we have new piping to them is all in Pex home runs.

    The baseboards that have been removed have push nipples. The push nipples look clean. They are 3/4" connectors. The end radiators have threaded connectors.

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  • Ironman
    Ironman Member Posts: 7,385
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    60 psi air is NOT equal to 60 psi water: it’s 2.31 times greater.

    In a dry sprinkler system, 45 psi is used to hold back 100 psi street water pressure. Like Jamie said, see if you can use water.

    Do you have the draw tool to re-assemble the BB sections?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • joseph annon
    joseph annon Member Posts: 53
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    I'll look into water pressure vs air pressure and present it to the inspector. I do not have a draw tool for the sections. What are the options for draw clamps? I will more than likely not need the tool again.

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  • mattmia2
    mattmia2 Member Posts: 9,828
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    some supply houses or online suppliers will rent or loan the tool
  • tim smith
    tim smith Member Posts: 2,770
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    no 60 psi air test, if one has weak casting it can be a claymore mine.
    joseph annonIronman
  • joseph annon
    joseph annon Member Posts: 53
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    Where can find something to support the need to use a water test instead of an air test. I have found a local contractor who will loan me his draw tool.

    There was an error rendering this rich post.

  • mattmia2
    mattmia2 Member Posts: 9,828
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    I believe you can find it in the plumbing code where it says it requires a hydrostatic pressure test
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,074
    edited March 2022
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    I think this publication should have your answer if you can find someone who has access to it.

    https://webstore.ansi.org/preview-pages/IAPMO/preview_IAPMO+IGC+332-2017a.pdf

    We used to test our hydronic installations on some jobs with air where water was not readily available. Often, the inspector demanded a hydrostatic test.

    On plumbing work, the UPC allowed a 4 psi air test which equals a 10 foot column of water above the highest fitting which is the normal test.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • KC_Jones
    KC_Jones Member Posts: 5,745
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    Where can find something to support the need to use a water test instead of an air test. I have found a local contractor who will loan me his draw tool.

    I’ll be honest, you shouldn’t need a code or a rule. It’s called common sense.

    If there is some kind of catastrophic failure at 60 PSI, the shrapnel can and will send someone to the emergency room, or the morgue. This isn’t a joke.

    Your inspector is dumb as a box of rocks. I feel no need to be polite in this situation considering the stupidity that is being expressed by that person.

    If one uses water that changes the entire discussion.

    The mention of 4 PSI is much more sensible.

    In all seriousness I can’t believe this conversation is happening.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
    Ironman
  • hot_rod
    hot_rod Member Posts: 22,327
    edited March 2022
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    Ironman said:

    60 psi air is NOT equal to 60 psi water: it’s 2.31 times greater.

    In a dry sprinkler system, 45 psi is used to hold back 100 psi street water pressure. Like Jamie said, see if you can use water.

    Do you have the draw tool to re-assemble the BB sections?

    I think psi is a unit of pressure, not density. 30 psi air = 30 psi of anything

    Now a column of water is where the 2.31 comes into it, maybe? .433 psi per foot of water column

    In a dry sprinkler system valve it's the surface area difference between the air and water side that allows a lower air side pressure.

    A lower psi air test is sometimes used as explained here.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    mattmia2Ironman
  • neilc
    neilc Member Posts: 2,711
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    it's that the air is compressible,
    so there's more of it to "let go" if bad things happen,
    you'll pump more air in the system than water to hit that 60 psi,
    air will go PUUSSHHH,
    water will just go pu_op
    known to beat dead horses